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212                         COPE ON THE TYPOTHERIA                       CHAP,

trochanter, and the unguiculate claws have already been referred
to. As to the latter, which are short, it is not the end phalanx
but the first which is retracted; thus Chalicotheriu'ni differs
markedly from both Carnivorous and Edentate types; for in the
former it is the last phalanx which is retracted, while in the
Edentates fche same phalanx is flexed downwards. The limbs of
ChaUcofherium are nearly of the same size, and the animal
seems to have been stout and quadrupedal.1

MacrotkeriuTn, like the last genus, seems to have been
common to both New and Old Worlds. It is to be distinguished
by a number of characters. It is supposed to have been " semi-
arboreal and fossorial"; the fore-limbs are much longer than
the hind, the relative proportions of the radius and tibia being
70 to 29. The ulna was distinct from the radius, whereas in
Chalicotfaeriu'm, the two are coalesced, or nearly so. Young
specimens appear to possess a full set of incisors; whether this
is the case or not with Ghalicotheri'um is not known.2

is sometimes placed in the group.

SUB-ORDEK 4.     TYPOTHERIA.
It is a little difficult to be confident that the Typotheria are
rightly referred to the Ungulata, since they contradict two im-
portant Ungulate rules. They have clavicles, which are elsewhere
missing, and the thumb looks as if it were opposable.3 An
Ungulate is essentially a running animal, and has no need of a
grasping finger. Still Typotheria are placed by most within the
Ungulate series, though their undoubted likenesses to other
groups, especially to the Bodentia, are admitted, and indeed
emphasised. Cope places them definitely with the Toxodonts.
The Typotheria are an extinct group of smallish beasts,
confined, like the Toxodontia, to South America, a region which
during the Tertiary period, and into the Pleistocene, abounded
with strange and varied types of Ungulate animals.
The earlier forms of Typotheria may be exemplified by some
1  See Osborn, American, JVa&uralzst, February 1893, p. 118.
2  It  is  not  absolutely  clear  whether both or only one genus ranged into
America.    Different opinions have been expressed.
* It must be remembered, however, that there is a suggestion of a prehensile
character in the hand of PAenacodus (see p. 203).